HEAT-INDUCED GEL FORMATION OF BETA-LACTOGLOBULIN - A STUDY ON THE SECONDARY AND TERTIARY STRUCTURE AS FOLLOWED BY CIRCULAR-DICHROISM SPECTROSCOPY

A variety of conditions affect the character of thermally induced beta-lactoglobulin (beta-LG) gels. The effects of these conditions on the secondary and tertiary structure of beta-LG during gel formation were studied by circular dichroism (CD) spectroscopy. Use of very short path length quartz cells (as low as 0.01 mm) allowed the in situ observation of gel formation. Salt concentrations and pH were not observed to significantly change the secondary structure composition, either before or after heating. It is important to note that no unfolded structure was detected during gel formation. However, an increase in residual tertiary structure was observed at higher salt concentrations after heating. The use of dithiothreitol to prevent disulfide bond formation was shown to significantly increase the beta-sheet content of beta-LG gels. Analysis of the CD spectra indicates that the secondary and tertiary structure of beta-LG are dependent on protein concentration, both before and after heating.